1) Need to build a small wheeled platform that traverses 95% of flat indoor floorings. ( I presume this leaves out tracked vehicles.)2) It needs to carry about 2.5 -3 lbs including its own weight.3) I will visually be able to drive it remotely.4) I plan to use a lead acid rechargable batt because I am guessing I will need a 2Ah battery (heavy..)

A) Is 4 wheel drive recomended?B) DC motor, stepper motor, or servo?C) Speed is not critical but what torque/ power would you guess is needed?

Thanks to all the experts here to set some initial criteria for my testing!

A) You don't really need a 4 wheel drive. I'd recommend using a differential drive, since it's a lot easier to construct.

B) All 3 kinds would work actually, although a DC motor might be too fast (unless it's a geared motor or you gear it down) to control remotely properly.

C) Hmm.. I'm not very good with torque calculations.

So, I recently built a differential drive robot with a single castor, that carries around 3 lbs of weight. I used 2 standard servos originally, and the speed for that was ok, although torque was kind of low. However, I used really big wheels which reduces the torque. So, for a robot carrying 2.5 - 3 lbs, those standard servos should work fine, especially if you get decent sized wheels unlike me

If you're intending to drive it remotely, it's probably better to go for a lower speed, unless you're really good with remote control cars Personally, I'm terrible at that so I have trouble controlling my robot even though it's not going very fast.

Trigger, not sure what you wanted me to see in the link, most of that information is pretty basic, so let me know if I missed something.

Somchaya,

Good info, this is helpful. What standard servos did you use? I agree on the difficulty driving remotely, especially since I have quite a bit of transport delay/ lag. Hitting a wall is bad, hitting a wall fast and far away is even worse...

Well, a 2-wheeled robot with a caster wheel is pretty stable, as long as you don't keep the weight balanced left/right. Well, I suppose if you turn really quickly there's a higher chance of falling, but usually that's not an issue

Diff drive robots are a lot easier to construct than their 4-wheel counterparts, esp if you want to use ackerman (i.e. car) steering methods..

If i was going to use the differental steering, but still have four wheels. Since my dc motor is not geared could i hook it up to a gear and also still a sprocket with a chain to the front wheel. my motor is an 18 volt

If i was going to use the differental steering, but still have four wheels. Since my dc motor is not geared could i hook it up to a gear and also still a sprocket with a chain to the front wheel. my motor is an 18 volt

Yeah that should be possible. I'm not exactly sure what you mean by "hook it up to a gear and also still a sprocket with a chain to the front wheel" though, but linking the two wheels on each side together with gears or chains is definitely possible.

Im planning on making a 2 wheeled robot (with support wheel)! it seems so easy just adding power to 1 of the wheel and not to the other for turning..!

Yep, diff drive robots are very easy in that regard.. However, after working with them a little, I realized it's a little troublesome when you want them to turn at a particular turn radius.. since you have to work with relative wheel speeds. A robot with ackerman steering would be easier in that way I think, since you can have separate inputs for robot speed, and robot turn angle..

Still, diff drive robots are much easier to work with in general I think..

On the robot i'm making now i have a turning mechanism where a little round toothed wheel is connected to a plastic board with to wheels in each end. When i add power the toothed wheel turn to one side and drift the wheel with it so it turns. But ti cant do very sudden turns.